Arches have many applications in different engineering fields and have been studied thoroughly complete. However, the behavior of an arch with a constraint plane is not well understood. This thesis employs the finite element method (FEM) to study the behavior of a pinned half-sine arch together with a constraint plane under a concentrated moment. Equilibrium positions and the associated stability of the arch under different conditions are investigated thoroughly. Due to the snap-through property and the appearance of the constraint plane, the load-axial force curve of the arch is quite complex and exhibits bifurcation phenomena. To confirm the results, the results of the FEM are compared with those of the modal analysis. We found that the results of the modal analysis provide useful information for determining the equilibrium positions of the arch using the FEM. The variation of the equilibrium positions with the applied load and values of system parameters are examined in detail. Finally, experimental apparatus is set up to validate the theoretical results.